Australian bird phenology: a search for climate signals

Temporal and climate‐related changes in avian phenology were assessed for seven species of south‐eastern Australia using data obtained from members of the public, naturalist groups and other organizations. Despite significantly warmer temperatures (～0.02–0.03°C per year) and reduced rainfall (～1.6–8.0 mm per year) over much of south‐eastern Australia in recent decades, most species showed no corresponding trends in their timing of migration or breeding, the notable exceptions being the grey fantail (Rhipidura fuliginosa) and the flame robin (Petroica phoenicea), which migrate through Melbourne, Victoria, during autumn and spring. In many species, however, migration or breeding timing appeared to be influenced to some extent by local, rather than regional, climate conditions, particularly local daily maximum and minimum temperatures. Whether these species will noticeably change their phenology to match projected changes in climate, perhaps when a currently unknown climate threshold is crossed, or whether these species are sufficiently flexible in their foraging strategies or food sources to be able to maintain their current timing, remains to be seen.     

Near-synchronous calling in the hip-pocket frog Assa darlingtoni

Sustained perfect synchrony of signal production by animals is unrealistic, but even near-synchronous signalling is extremely rare. Near-synchronous signalling has been documented in some orthopteran insects and fireflies, and one kind of frog. This study provides observations and analyses of sustained bouts of impressive near-synchronous calling by a terrestrial breeding frog from Australia, the hip-pocket frog (Assa darlingtoni). Males called in scattered clusters of several individuals from the rainforest floor of northern New South Wales. In eight of nine pairs of semi-isolated males, there was sustained near-synchronous calling in bouts consisting of 16–20 calls and lasting 5–10 min. There was extensive overlap of the pulsed calls, and calls of a lagging male began overlapping that of a leading male after 2–5 pulses of a leader’s call note. In five pairs, one male’s calls were usually in the leading position; in three pairs, leadership frequently switched between males. In the latter interactions, males frequently skipped a call and produced its next call or calls in the leading position. This tactic has been interpreted as sexual competition between neighbours in orthopterans, but further research is required to rule out possible alternative hypotheses.     

Interannual variation in reproductive phenology in a riverine fish assemblage: implications for predicting the effects of climate change and altered flow regimes

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Population trends and calling phenology of anuran populations surveyed in Ontario estimated using acoustic surveys

Many acoustic surveys have been initiated to monitor anuran populations in North America. We used the Ontario Backyard Frog Survey to examine temporal and spatial trends, from 1994 to 2001. Our data suggest that there have been no consistent trends in site occupancy during this time period, but there were some differences among years. Both American toads and northern leopard frogs were more prevalent in 1995 than in 1994. Similarly, species richness was higher in 1995 and 1996 compared to most other years. Individual populations of species, however, often were not stable. Extinction and colonization rates varied among species, and ranged from 1.5 to 19.5% per year, and site occupancy was negatively correlated with extinction rates. Daily detection probabilities were often quite low, and were primarily driven by the perceived calling intensity. We recommend: (i) that monitoring programs attempt to preserve common survey routes, despite heavy turnover of volunteers, (ii) calling surveys be timed to maximize detection probabilities, and (iii) analyses based upon landscape features and GIS approaches should be used to determine localized changes in site occupancy or species richness.     

Flowering phenology of a palm community in a central Amazon forest

The flowering phenology of 27 taxa of palms in a lowland moist forest in the central Amazon was recorded over a 40 month period. Phenological data were transformed into measures, of synchrony, regularity, and duration. Flowering was observed at all times of year and there was no correlation with rainfall either for the current month or for any monthly lag interval. The 27 taxa were divided into three pollination groups—weevil, bee/fly, or beetle—based on their behavior at anthesis. Phenology was significantly correlated with pollination groups. Weevilpollinated palms had higher synchrony and shorter duration of flowering than other groups. Bee/fly-pollinated palms had lower synchrony and longer duration of flowering. The beetle-pollinated palms were intermediate between the two other groups. Seasonal regularity of flowering was similar in all three groups. We suggest that, at least inBactris, taxa exhibit staggered flowering.     

Predicting a change in the order of spring phenology in temperate forests

The rise in spring temperatures over the past half‐century has led to advances in the phenology of many nontropical plants and animals. As species and populations differ in their phenological responses to temperature, an increase in temperatures has the potential to alter timing‐dependent species interactions. One species‐interaction that may be affected is the competition for light in deciduous forests, where early vernal species have a narrow window of opportunity for growth before late spring species cast shade. Here we consider the Marsham phenology time series of first leafing dates of thirteen tree species and flowering dates of one ground flora species, which spans two centuries. The exceptional length of this time series permits a rare comparison of the statistical support for parameter‐rich regression and mechanistic thermal sensitivity phenology models. While mechanistic models perform best in the majority of cases, both they and the regression models provide remarkably consistent insights into the relative sensitivity of each species to forcing and chilling effects. All species are sensitive to spring forcing, but we also find that vernal and northern European species are responsive to cold temperatures in the previous autumn. Whether this sensitivity reflects a chilling requirement or a delaying of dormancy remains to be tested. We then apply the models to projected future temperature data under a fossil fuel intensive emissions scenario and predict that while some species will advance substantially others will advance by less and may even be delayed due to a rise in autumn and winter temperatures. Considering the projected responses of all fourteen species, we anticipate a change in the order of spring events, which may lead to changes in competitive advantage for light with potential implications for the composition of temperate forests.     

Niche overlap in allotopic and syntopic populations of sexually interacting ground‐hopper species

Abstract There is accumulating evidence that sexual interactions among species (reproductive interference) could have dramatic effects for species’ coexistence. It has been shown that the fitness of individuals can be substantially reduced as a consequence of reproductive interference. This might subsequently lead to displacement of a species (sexual exclusion). On the other hand, some evolutionary and ecological mechanisms might enable species to coexist, such as the divergence of mate recognition systems (reproductive character displacement), habitat partitioning, clumped dispersion patterns or different colonization capabilities. We have previously shown that the two ground‐hopper species Tetrix subulata and Tetrix ceperoi interact sexually in the laboratory as well as in the field. At sites where both species co‐occur niche overlap was high, suggesting that coexistence is maintained by different niche breadths rather than by habitat partitioning. To test the hypothesis that habitat partitioning does not contribute to species’ coexistence, we examined whether allotopic and syntopic populations of these two species differ in niche overlap (competitive release). Our results show that niche overlap is higher in syntopic than in allotopic populations, suggesting that the site‐specific habitat structure (heterogeneity) has a stronger influence on microhabitat utilization than the presence of heterospecifics. Hence, our data do not support the hypothesis that habitat partitioning plays a substantial role for the coexistence of these sexually interacting species.     

Limited niche differentiation within remarkable co‐occurrences of congeneric species: Monomorium ants in the Australian seasonal tropics

Niche theory predicts that few closely related species can co‐occur because such species tend to be ecologically similar and niche differentiation is required to avoid competitive exclusion. We analyse the co‐occurrence of a remarkable 10–15 species of the ant genus Monomorium occurring within single 10 × 10 m plots in a tropical savanna of northern Australia. Most of the species are undescribed, so we use genetic analysis to validate our species demarcations. We document nest dispersion patterns, and investigate differentiation in the three primary niche dimensions: space, time and food. We also examine species differences in competitive abilities, by describing rates of foraging activity, foraging ranges, worker aggression, and levels of behavioural dominance. Analyses of nest and forager distributions showed very limited evidence of spatial segregation within plots. The great majority of species foraged either exclusively or primarily during daylight hours. Body size and isotopic analyses indicated very limited dietary differentiation. Such limited niche partitioning occurred despite the species differing markedly in their competitive abilities as measured by rates of resource discovery, recruitment and monopolization. Our findings defy the traditional assumption that multiple closely related and ecologically similar species of highly interactive taxa cannot co‐occur. It seems very likely that species coexistence in our study system is determined to a very large degree by stochastic processes relating to dispersal and establishment, as predicted by neutral theory. However, neutral theory assumes competitive equivalence, whereas we found very marked differences in the competitive abilities of our co‐occurring species. We suggest that competitive exclusion is prevented by the modular nature of ant colonies, with competition limiting colony performance but not preventing occurrence. We conclude that other factors that allow species persistence, and not just competitive equivalence, can allow dispersal and establishment processes to drive species coexistence.     

Habitat-dependent advertisement call variation in the monkey frog Phyllomedusa nordestina

The acoustic adaptation hypothesis (AAH) predicts that acoustic signals are selected to propagate more efficiently in the habitat where they are normally transmitted. Several studies corroborated the AAH for primates and birds, but evidence for frogs is contentious: While most studies failed to support the AAH, recent studies have shown that within-species variation conforms to the predictions of the AAH. Herein, we test the AAH by comparing advertisement calls of Phyllomedusa nordestina from two contrasting habitats (Atlantic Rainforest and Caatinga) and by testing the influence of the amount of vegetation around calling sites on acoustic parameters of frog calls. The interval between pulses was significantly different between individuals from the Atlantic Rainforest and from the Caatinga, and the number of pulses was correlated with the amount of vegetation around calling sites. Hence, our results indicate that multiple evolutionary forces may act simultaneously on the advertisement calls of frogs.     

东北地区植被物候时序变化

植被与气候的关系非常密切,植被物候可作为气候变化的指示器。东北地区位于我国最北部,是气候变化的敏感区域,研究该区植被物候对气候变化的响应对阐明陆地生态体统碳循环具有重要意义。利用GIMMS AVHRR遥感数据集得到了东北地区阔叶林、针叶林、草原和草甸4种植被25a(1982—2006年)的物候时序变化,得出4种植被春季物候都表现出先提前后推迟的现象,秋季物候的变化则比较复杂,阔叶林和针叶林整体上呈现出秋季物候推迟的趋势,草原和草甸则表现为提前-推迟-提前的趋势。应用偏最小二乘(Partial Least Squares)回归分析了该区域植被物候与气候因子之间的关系,结果表明:春季温度与阔叶林、针叶林和草甸春季物候负相关,前一年冬季温度与草原春季物候正相关,降水与植被春季物候的关系有点复杂;4种植被秋季物候与夏季温度均呈正相关,除草原外,其余3种植被秋季物候均与夏季降水负相关。植被春季物候可能主要受温度影响,而秋季物候很可能主要受降水控制。     

Genetic variation of the bud and leaf phenology of seventeen poplar clones in a short rotation coppice culture

Abstract: Leaf phenology of 17 poplar ( Populus spp.) clones, encompassing spring phenology, length of growth period and end-of-year phenology, was examined over several years of different rotations. The 17 poplar clones differed in their latitude of origin (45°30'N to 51°N) and were studied on a short rotation experimental field plantation, situated in Boom (province of Antwerpen, Belgium; 51°05'N, 04°22'E). A similar, clear pattern of bud burst was observed during the different years of study for all clones. Clones Columbia River, Fritzi Pauley, Trichobel (Populus trichocarpa) and Balsam Spire (Populus trichocarpa × Populus balsamifera) from 45°30'N to 49°N reached bud burst (expressed as day of the year or degree day sums) almost every year earlier than clones Wolterson (Populus nigra), Gaver, Gibecq and Primo (Populus deltoides × Populus nigra) (50°N to 51°N). This observation could not be generalised to end-of-season phenology, for which a yearly returning pattern for all clones was lacking. Late bud burst and early leaf fall of some clones (Beaupré, Boelare, IBW1, IBW2, IBW3) was brought about by increasing rust incidence during the years of observation. For these clones, the variability in leaf phenology was reflected in high coefficients of variation among years. The patterns of genetic variation in leaf phenology have implications for short rotation intensive culture forestry and management of natural populations. Moreover, the variation in phenology reported here is relevant with regard to the genetic mapping of poplar.     

If a frog calls in the forest: Bioacoustic monitoring reveals the breeding phenology of the endangered Richmond Range mountain frog (Philoria richmondensis)

Amphibians are the most threatened vertebrate taxon of modern times. Baseline data and affordable methods to monitor populations are absent for many Australian frog species. Furthermore, some species are visually cryptic, and detection often relies upon male advertisement calls. Imperfect detection rates impede our ability to assess the status of populations over time. Understanding the factors that influence calling is essential to inform the timing of survey effort and increase survey efficiency. Automated recording systems offer considerable potential to determine calling phenology and establish the relationship between calling and abiotic factors. The mountain frogs (Philoria Myobatrachidae) of the Gondwana rainforests are considered susceptible to climate change impacts, such as shifts in the timing of calling. In order to describe the calling phenology of Philoria richmondensis, commercially available automated recording systems were deployed at five locations, and over 5000 h of sound recordings were captured and analysed. Peak calling activity occurred during morning and evening periods in the austral spring. Ambient temperature was found to significantly contribute to the probability of a call occurring, with the highest frequency of calls recorded occurring between 15°C and 16°C, and there was a negative relationship between precipitation and calling activity. The results allow future surveys to be better targeted and provide a benchmark with which to detect changes in calling phenology over time.     

Spatial indicators of plant community assembly from a 453-year sand-dune chronosequence

Background : We explored evidence for spatial patterning in vegetation across a sand-dune chronosequence spanning 453 years of primary succession to test for indications of a temporal signature of niche versus neutral processes during community assembly.

Methods : The study was conducted on a series of dune-capped beach ridges located in Wilderness State Park in Emmet County of northern Lower Michigan, United States (45° 43′ N, 84° 56′ E). Nearest-neighbour survey data were subjected to species dispersion and association analyses.

Results : Both species richness and species evenness showed the classic ‘hump-shaped’ relationship across successional time, suggesting that competition is an important force in structuring this community. However, the only evidence of intra-specific aggregation occurred in the youngest dune. Older dunes displayed random spatial structure and the oldest dunes tended toward a mix of random patterns and intra-specific segregation, i.e. with nearest neighbours more likely than by chance to be inter-specific. In addition, the frequency of species having lower neighbour-species richness than expected by chance was higher in younger, not older dunes. Species with significantly low neighbour richness (based on absolute nearest neighbours) on later dunes tended to have a high proportion of nearest neighbours that were intra-specific.

Conclusions : The data provided no evidence that resident species in later succession have greater intra-specific aggregation or more niche differentiation based on horizontal niche space. The data are more consistent with theories of community assembly involving competitive equivalence and/or effects of facilitation.     

Microgeographic countergradient variation in the wood frog, Rana sylvatica

Prior studies have shown that macrogeographic gradients in temperature associated with latitude and altitude can lead to countergradient patterns of variation in a number of taxa: individuals from colder environments are known to grow or develop faster than their conspecifics from warmer environments when placed in a common setting. In this study, I hypothesized that countergradient variation also is important at microgeographic scales. The wood frog, Rana sylvatica, breeds in open-canopied, temporary wetlands as well as those heavily shaded by vegetation. Shading leads to cooler thermal environments that are associated with embryonic development rates as much as 50% slower than those in unshaded wetlands. Wetlands with contrasting canopy environments are often found within tens or hundreds of meters of each other. In a common garden experiment, embryos from nearby natural wetlands displayed countergradient variation: individuals collected from shaded wetlands developed up to 12% faster than those collected from relatively unshaded wetlands. The results of this study suggest that the concept of countergradient variation may be extended to small scales of space. In addition, the rate and scale of vegetation dynamics (the agent of wetland shading) imply that divergence in development among residents of nearby wetlands may be relatively rapid, on the order of decades.     

Arginine vasotocin activates advertisement calling and movement in the territorial Puerto Rican frog, Eleutherodactylus coqui

Arginine vasotocin (AVT) is a neuropeptide that modulates social behavior in amphibians and activates calling in frogs. The Puerto Rican coqui frog, Eleutherodactylus coqui, is a terrestrial anuran that exhibits complex social behaviors, including territoriality and paternal care. Males have a distinctive social hierarchy and can be any of the following: satellite (non-calling), territorial (calling), or paternal (guards and broods embryos). Field experiments were conducted to determine the effects of AVT on satellite behavior and the male social hierarchy of E. coqui. Satellite males were captured within the territory held by a resident male, given injections (i.p.) of AVT or saline (control) and placed back in their original location. To determine if AVT affects all males, not merely satellite males, territorial (calling) males were injected with AVT. Significantly more satellite males commenced advertisement calling following AVT injections than did control males injected with saline. AVT-activated satellites did not challenge the resident territorial male for possession of the territory but instead moved into a new area before commencing to call. In fact, AVT-activated satellite males were significantly more likely to move into a new territory following AVT injections than AVT-injected territorial males. The effect of AVT was short lived, lasting only one night in all but two cases. It is concluded that AVT stimulates advertisement calling and AVT-activated males displayed territorial characteristics of E. coqui.